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Employee Future Benefits - Summary of Re-measurement Effects Recognized in Other Comprehensive Income (Detail) - CAD ($)
$ in Millions
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Pension defined benefit plans [member]    
Disclosure of defined benefit plans [Line Items]    
Experience $ (5) $ (3)
Demographic assumption changes   (7)
Economic assumption changes 835 194
Return on plan assets (excluding interest income) (869) 70
Change in effect of asset limit (excluding interest) (10) (37)
Total re-measurement effects (49) 217
Retiree welfare plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Experience 13  
Demographic assumption changes   (1)
Economic assumption changes 112 29
Return on plan assets (excluding interest income) (91) (1)
Total re-measurement effects $ 34 $ 27